1. Field of the Invention
The present invention relates to a base member for a liquid discharge head for discharging a liquid, a liquid discharge head utilizing the base member, and producing method therefor.
2. Description of the Related Art
A liquid discharge head for discharging a liquid from a liquid discharge port is used popularly, particularly as an ink jet head for use in an ink jet recording apparatus (ink jet printer). A producing method for such ink jet head is disclosed for example in Japanese Patent Application Laid-Open No. H06-286149.
In the ink jet head as an example of the liquid discharge head, a higher resolution of recording, a higher image quality and a higher speed are being recently requested. Among these requirements, a solving method for the requirements for higher resolution and higher image quality is proposed in making a smaller liquid amount of the discharged ink per dot (in case of discharging the ink as a droplet, making a smaller-sized droplet). In an ink jet head for discharging the ink by thermal energy as disclosed in the aforementioned patent reference, the smaller droplet size of the ink has been accomplished by reducing an area of a heat-generating part and by changing the shape of a nozzle (reducing the area of the ink discharge port).
In order to realize such smaller liquid droplet in the ink discharge amount, the ink discharge port has to be formed precisely. However, when a flow path forming member constituting an ink flow path wall and an ink discharge port is formed by a resinous material, as disclosed in Japanese Patent Application Laid-open No. H06-286149, the resinous material may exhibit a swelling by the ink or the like, thereby causing a deformation of the ink discharge port. In the past, such deformation has been minimal and has not been considered as a problem. However, in order to obtain an image of a higher quality with a higher speed, there is required a substrate for the ink jet head, bearing a plurality of discharge ports without such deformation.
Also the resinous material and the base member may become liable to show a peeling at the surface of the base member, resulting from the aforementioned deformation of the resinous material by the ink or from a deterioration caused by a chemical reaction with the ink component itself.
Also the flow path forming member, being formed by a photosensitive resin material, may cause a deformation by an unevenness in the exposure or by a reflection from an underlying layer, thereby becoming unable to precisely form the discharge port of a small area, corresponding to a small liquid droplet. Therefore, in order to form a discharge port matching a small liquid droplet and capable of reducing an ink mist, it is being investigated to utilize so-called dry etching technology such as reactive etching or plasma etching, instead of the photolithographic technology utilizing exposure and development of a photosensitive resin. More specifically, considered is a dry etching, utilizing an inorganic film such as a SiOC film, having a larger selectivity at etching in comparison with the flow path forming member, as a mask. However, since the conventional film forming method (for example plasma CVD) involves a high substrate temperature of from 200 to 300° C. or even higher at the film formation, the flow path forming member formed with a resinous material becomes deformed. Therefore, for executing an etching for forming the discharge port on the upper surface of the flow path forming member, a mask material has to be a material which can be formed at a low temperature that does not cause the deformation of the flow path forming member.
On the other hand, in order to obtain discharge characteristics capable realizing a further improved recording quality, it is desirable that the internal wall (internal surface) of the ink flow path is substantially hydrophilic, and that an external surface area of the flow path forming member, including the aperture of the ink discharge port, has a water-repellent property. Particularly in order to suppress a deformation in the ink discharge port, it is desirable to avoid a swelling, by the ink, of a surface in which the ink discharge port is opened (a discharge port-containing face of the ink jet head, opposed to a recording medium in the recording operation).